We have a Korky 528 Anti-Siphon on our toilet, and it recently started making a noise that sounds like a mix between something going "tukatukatuka" and a steam locomotive barreling down the rails. I'm not sure what's wrong, and strangely enough Googling "Korky 528 anti-siphon tukatuka" doesn't exactly come up with any great results. Any help? You can hear it throughout the house it's so loud.